1. Field of the Invention
This invention relates generally to measuring thin film thicknesses in semiconductor device fabrication. In particular, this invention relates to measuring the thickness of a bottom anti-reflective coating (BARC) over a plurality of holes in a layer of a semiconductor device.
2. Description of the Related Art
A continuing trend in semiconductor devices is the reduction of feature size to decrease the distance between components on devices and thus increase device speed and computational power of devices. As feature size shrinks to submicron size, traditional optical methods of resolving features become less precise.
Optical scatterometry does provide a method of determining small features in semiconductor processing. Exemplary of prior art scatterometry measurements in the context of semiconductor processing are: Christopher J. Raymond et. al., xe2x80x9cMetrology of Subwavelength Photoresist Gratings Using Optical Scatterometryxe2x80x9d, Journal of Vacuum Science and Technology, B, Vol. 13(4), July/August, pp. 1484-1495 (1995); Ziad R. Hatab et. al., xe2x80x9cSixteen-megabit Dynamic Random Access Memory Trench Depth Characterization Using Two-dimensional Diffraction Analysisxe2x80x9d, Journal of Vacuum Science and Technology, B, Vol. 13(2), March/April, pp. 174-182 (1995); and U.S. Pat. No. 5,876,276 to McNeil et al.
According to an embodiment of the present invention there is provided a method for forming a semiconductor device. The method includes providing a semiconductor substrate with a first layer, the first layer having a first surface and a plurality of holes therein; forming a bottom antireflective coating (BARC) in the plurality of holes and on the first surface; performing a scatterometry measurement on at least a portion of the BARC to produce measurement diffraction data; predicting a thickness of the BARC in the plurality of holes by comparing the measurement diffraction data to a model of diffraction data to provide a predicted thickness, tp, and determining if the predicted thickness, tp, is within a target thickness range, xcex94tt; and controlling the BARC forming step in response to the BARC thickness predicting step.
According to another embodiment of the present invention there is provided a thickness control device that controls the thickness of a bottom anti-reflective coating (BARC) in a plurality of holes in a layer on a semiconductor substrate. The device includes a scatterometer that produces scatterometry diffraction data of the BARC; a computational unit operative for predicting the thickness of the BARC in the plurality of holes by comparing the diffraction data of the BARC to a model of diffraction data to provide a predicted thickness, tp; and a process controller receiving the predicted thickness from the computational unit for controlling the thickness of the BARC in the plurality of holes to be within a target thickness range, xcex94tt.